Ole Rømer
Ole Rømer died on the 19th September 1710.
He was
born on September 25, 1644, in Århus, Denmark, little is known of his early
life, however he was invited to join the observatory at Uraniborg to work on observations made by Tycho Brahe from
1664-1670.
In 1671 over a period of several months, Jean Picard and
Rømer observed about 140 eclipses of Jupiter's moon Io, while in Paris Giovanni
Domenico Cassini observed the same eclipses. By comparing the times of the
eclipses, the difference in the longitudes of Paris and Uraniborg was
calculated.
Rømer noticed upon examination of the data that he collected
along with the observations of Cassini that the times at which the satellite Io
emerges from the shadow of Jupiter in each of its revolutions about the planet
are continually lengthened as the earth recedes from Jupiter, while in a
similar but reverse manner, the times between emergences are shortened as the
earth approaches Jupiter.
Rømer did not actually calculate the speed of light from his
observations. At the time, the distance between the sun and the earth was still
only a roughly calculated quantity, while the earth's elliptical path around
the sun meant that the distances between the earth and Jupiter did not accrue
uniformly, but varied in a complex manner according to the time of year and the
position of the earth in its orbit. It would be left to later investigators to
pin down an actual speed of light based on these phenomena.
In his Mathematical Principles of Natural Philosophy (1713),
Isaac Newton credits Rømer as the first to observe the velocity of light
through observations of Jupiter's moons.
No comments:
Post a Comment